The present invention relates to a rotational angle detector, and more particularly, to a rotational angle detector for detecting the rotational angle of, for example, a gearshift lever of an automobile.
FIG. 1 is a schematic front view showing a prior art rotational angle detector 50, and FIG. 2 is a cross-sectional view of the rotational angle detector 50.
The rotational angle detector 50 includes an annular magnet 51 rotated integrally with a gearshift lever (not shown). The magnet 51 is magnetized so that its magnetic flux extends in a direction perpendicular to the front and rear surfaces of the magnet 51. In other words, the magnet 51 is polarized in the axial direction of the magnet 51 (direction perpendicular to the plane of FIG. 2). Accordingly, the magnetic flux extends upward or downward with respect to the plane of FIG. 2 at locations near the front and rear surfaces of the magnet 51.
A magnetic resistance sensor 52 is arranged at a position corresponding to the center of the magnet 51 to detect direction changes of the magnetic flux of the magnet 51. When the gearshift lever is shifted and the magnet 51 is rotated by a predetermined angle, the magnetic resistance sensor 52 generates an analog output voltage in accordance with the direction of the magnetic flux, which changes in accordance with the rotational angle of the magnet 51. More specifically, referring to FIG. 3, the analog output voltage has a waveform that is generally a sine wave. The linear portion of the output voltage wave is the detection range of the gearshift lever rotational angle.
In the conventional rotational angle detector 50, the linear portion of the analog output voltage waveform (sine wave) output from the magnetic resistance sensor 52 is short. Thus, the detection range of the rotational angle is less than 90xc2x0. The conventional rotational angle detector 50 thus cannot be employed if a detection range of 90xc2x0 or more is required. Further, since a shaft connected with the gearshift lever is inserted through the middle of the magnet 51, the positioning of the magnetic resistance sensor 52 along the axis of the magnet 51 is difficult.
It is an object of the present invention to provide a rotational angle detector that enlarges the detection range and facilitates the positioning of the magnetic resistance sensor.
To achieve the above object, in a first perspective, the present invention is a detector for detecting a rotational angle of a detected object. The detector includes a magnet having a surface. The magnet forms a magnetic flux in a predetermined direction along the surface. A magnetic resistance sensor generates a detection signal corresponding to the direction of the magnetic flux. The detected object is connected to one of the magnet and the magnetic resistance sensor, and the magnet and the magnetic resistance sensor are rotated relative to each other to generate the detection signal and obtain the rotational angle of the detected object. The magnetic resistance sensor is spaced from an axis of rotation of one of the sensor and the magnet.
In a further perspective, the present invention is a detector for detecting a rotational angle of a detected object. The detector includes an annular magnet for forming a magnetic flux parallel to a predetermined radial direction of the magnet. A magnetic resistance sensor generates a detection signal corresponding to the direction of the magnetic flux. The detected object is connected to one of the magnet and the magnetic resistance sensor, and the magnet and the magnetic resistance sensor are rotated relatively to each other to generate the detection signal and obtain the rotational angle of the detected object. The magnetic resistance sensor is separated from an axis of rotation of one of the sensor and the magnet.
In another perspective, the present invention is a detector for detecting a rotational angle of a detected object. The detector includes an annular magnet for forming a magnetic flux in a radial direction of the magnet. The magnet includes a first magnetic pole portion and a second magnetic pole portion located on the outer side of the first magnetic portion. The first magnetic pole portion has a north pole and a south pole, and the second magnetic pole portion has a south pole located in correspondence with the north pole of the first magnetic pole portion and a north pole located in correspondence with the south pole of the first magnetic pole portion. A magnetic resistance sensor generates a detection signal corresponding to the direction of the magnetic flux. The detected object is connected to one of the magnet and the magnetic resistance sensor, and the magnet and the magnetic resistance sensor are rotated relatively to each other to generate the detection signal and obtain the rotational angle of the detected object. The magnetic resistance sensor is separated from an axis of rotation of one of the sensor and the magnet.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.